Alcohols, supercritical removal

In another method, developed by Jacobucd and co-workers (9), alcohol is removed by supercritical CO2 extraction in a semi-continuous system. 

Drying Here, water and alcohol are removed at moderate temperatures (<470K), leaving a hydroxylated metal oxide with residual organic content. If the objective is to prepare a high surface area aerogel powder of low bulk density, the solvent is removed supercritically. 

SFE was studied for the removal of free alcohol from dodecanol ethoxylate. Supercritical CO2, especially CO2 containing a few percent methanol, was selective for removal of the alcohol and the lower homologs. However, the distribution coefficients were such that an extraction which removed all of the free alcohol also removed 70% of the ethoxylates. Propane and ammonia may be substituted for C02/Me0H, with similar results (90). 

Using inorganic salts as precursors, alcohol as the supercritical drying agent, and a batch process a solvent-exchange step was necessary to remove water from the gel. 

The high-pressure cells and temperature control units are similar to the ones described by Betts and Bright (29). Samples for analysis were prepared by directly pipetting the appropriate amount of stock solution into the cell. To remove residual alcohol solvent, the optical cell was placed in a heated oven (60 °C) for several hrs. The cell was then removed from the oven, connected to the high-pressure pumping system (29), and a vacuum (50 pm Hg) maintained on the entire system for 10-15 minutes. The system was then charged with CF3H and pressurized to the desired value with the pump (Isco, model SFC-500). Typically, we performed experiments at 10 /xM PRODAN and there was no evidence for primary or secondary interfilter effects. HPLC analysis of PRODAN subjected to supercritical solvents showed no evidence of decomposition or additional components. 

Removal of Organic Sulfur from Coal by Reaction with Supercritical Alcohols... 

Growing concern over environmental effects of acid rain has resulted in increased Interest in development of pre-combustion removal of sulfur from coal. Physical coal cleaning processes are effective for pyritic sulfur removal but do little to reduce the organic sulfur content of coal This paper reports the removal of organic sulfur from coal, employing ethyl or methyl alcohols as the solvent/ reactant. The process is based on the observation that, under supercritical conditions, reactions occur that selectively remove organic sulfur from the coal matrix. 

Sulfur forms analyses on the product solids are not reported here, since results of the ASTM standard procedure can be misleading in terms of Indicating which type of sulfur (pyritic, sulfate, organic) has been removed. Typically, both sulfate and pyritic sulfur are Indicated to be present in low concentrations (generally less than 0.2%) when the ASTM procedure is applied to the solid product from supercritical desulfurization of coal with alcohols. 

Supercritical Drying of the Alcohol In this method, the system is first pressurized with CC>2 and CC>2-Alcohol mixture is brought to a supercritical condition and the supercritical fluid is removed slowly from the gel. The experimental set-up for this system is shown in Figure 2. 

Supercritical Water Oxidation (SCWO) has been proved to be a suitable process for treatment of several toxic and hazardous organic wastes due to its high removal efficiency. SCWO requires of hard reaction conditions (22.1 MPa and over 374°C). Special reactors are needed to support these conditions. An original reactor design is presented here wich has been tested in the treatment of alcohols+ammonia solutions in water. Performance results are presented here for ammonia and alcohols. Destruction efficiency greater than 99.9% are reached for both compounds, probing the correct performance of the reactor. 

Usually, the terpenes are removed from the cold-pressed oils (deterpenation) to concentrate the flavour fraction, thus resulting in a more stable product with improved solubility in the alcoholic solvents used in food and perfume processing. Supercritical carbon dioxide extraction appears as a promising and alternative technique to refine cold-pressed citrus oils [1,2, 3). Potentially, it has the advantages that it can be carried out at mild temperatures, provides better yields and leaves no solvent residues. 

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